The present invention relates to plastic containers, preferably for non-carbonated food products, based on high density polyethylene (HDPE). More particularly, the present invention relates to molded plastic containers based on HDPE, having barrier properties and having a carbon-coated internal surface.
It is highly desirable to provide plastic containers having barrier properties, and it is also highly desirable to provide plastic containers using HDPE. HDPE is more like a regular crystal than the amorphous tangle of the polymer chains in low density polyethylene (LDPE). Also, HDPE is stronger and stiffer than LDPE. However, HDPE generally does not have barrier properties and has poor oxygen permeation rates. Therefore, despite the economic desirability of using HDPE, the use of such material has not been practical.
It would be particularly desirable to use HDPE for containers for non-carbonated food products, as beverages, due to its low cost and desirable properties if one could devise an effective and low cost way of overcoming the high porosity of this material.
Multi-layer plastic containers are commonly used for packaging items in a wide range of fields, including food and beverage, medicine, health and beauty, and home products. Plastic containers are known for being easily molded, cost competitive, lightweight, and generally suitable for many applications. Multi-layered containers provide the benefit of being able to use different materials in each of the layers, wherein each material has a specific property adapted to perform a desired function.
Because plastic containers may permit low molecular gases, such as oxygen and carbon dioxide, to slowly permeate through their physical configurations, the use of plastic containers sometimes proves to be less desirable when compared to containers formed from other less permeable materials, such as metal or glass. In most applications, the shelf life of the product contents is directly related to the package""s ability to effectively address such molecular permeation. In the case of non-carbonated beverages, such as juices, oxygen in the atmosphere surrounding the container can gradually permeate inwardly through the plastic walls of the container to reach the inside of the container and deteriorate the contents. A highly porous container such as HDPE can permit rapid deterioration of the flavor of the container contents.
To address some to the foregoing concerns, plastic container manufacturers have utilized various techniques to reduce or eliminate the absorption and/or permeability of such gases. Some of the more common techniques include: increasing the thickness of all or portions of the walls of the container; incorporating one or more barrier layers into the wall structure; including oxygen-scavenging or reacting materials within the walls of the container; and applying various coatings to the internal and/or external surface of the container. However, a number of conventional barrier and/or scavenger materials will not effectively curtail permeation through a highly porous container wall, especially over extended periods of time. Moreover, there are usually other practical concerns associated with most conventional techniques, most commonly, increased material costs and/or production inefficiencies.
In recent times, the use of plastics has become a significant social issue. Recycling has become an increasingly important environmental concern and a number of governments and regulatory authorities continue to address the matter. In a number of jurisdictions, legislation pertaining to the collection, return, and reuse of plastic containers has either been considered or has already been enacted.
Moreover, HDPE is a particularly desirable material, especially for non-carbonated food products, as beverages, due to its desirable properties. For example, it has high strength and is of low cost. It can be readily used with color concentrates to provide an attractive colored product which will also reduce or eliminate the harmful effects of ultra-violet light. Moreover, it can be effectively used with a wide variety of color concentrates. It has good processability and good shrinkage properties.
Therefore, a need exists in the industry and it is an object of the present invention to provide a plastic container based on HDPE especially a container that is suitable for holding non-carbonated beverages, such as juices, and provide an acceptable level of performance when compared to commercial containers formed from alternative materials. A further need exists for a method to produce such containers in high volume commercial rates using conventional equipment.
It is a still further object of the present invention and need to provide a container based on HDPE which has barrier properties and which minimizes or avoids the high cost of inconvenience of conventional multi-layer plastic containers. It is a still further objective to do this at a reasonable cost, in a commercially feasible process, and with an effective product.
It has been found that the foregoing objects and advantages are readily obtained in accordance with the present invention.
Recognizing the problems and concerns associated with conventional multi-layered plastic containers, especially those used to hold non-carbonated food products, especially beverages, a plastic container having enhanced gas barrier properties and based on HDPE is advantageously provided. A container constructed in accordance with the principles of the present invention provides several advantages over those previously available. Such advantages are generally realized through the use of the desirable HDPE and a carbon coating on the internal surface of the container. It is a significant advantage that the container of the present invention desirably may also include oxygen scavengers and may have a multi-layered configuration. Furthermore, the improved container can be produced using conventional processing techniques and manufacturing equipment.
An important aspect of the present invention is the effective barrier properties of the present container with the functional and commercial benefits associated with having a container including the desirable HDPE. Further, the ease in subsequently recycling a container produced in accordance with the principles of the present invention make the practice of the invention extremely advantageous. Moreover, the present invention provides the additional advantage of permitting the manufacturer to controllably vary the material positioning and wall thickness at any given location along the vertical length of the inner and/or outer layers of the container.
In accordance with the principles of the present invention, a container is provided which is particularly suitable for non-carbonated food products, as beverages, which may be blow molded or extrusion molded, having an upper wall portion, an intermediate sidewall portion positioned beneath the upper wall portion, and a base portion positioned beneath the intermediate sidewall portion, the base portion being adapted to dependently or independently support the container. The container includes a molded first layer having an inner surface and an outer surface formed from high density polyethylene and a carbon coating formed adjacent and desirably on the inner surface of the first outer layer and adhered thereto and substantially coextensive with the first layer. In a preferred embodiment, the thickness of the first layer is controllably adjusted along its vertical length. If desirable, the first layer may also include additional barrier materials and/or oxygen scavenging/reacting materials incorporated therein.
In accordance with the principles of the present invention, the container may include a second layer adjacent the first layer, wherein the second layer is adjacent at least one of the inner surface of the first layer and the outer surface of the first layer, to provide a highly desirable, multi-layered container.
The HDPE used in the present invention has a density above about 0.940 grams/cc.
The container of the present invention is particularly suitable for use with non-carbonated products as food products, but may also be used for products which advantageously include the injection of gases therein, as CO2 or nitrogen.
Other and further advantages and novel features of the invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings, wherein, by way of illustration and example, embodiments of the present invention are disclosed.